Gas sample injection apparatus



April 1, 1969 w, GERDES 3,435,661

GAS SAMPLE INJECTION APPARATUS Filed Jan 6. 19 67 INVENTOR. Wa/fer F.Gare e5 HGENT United States Patent 3,435,661 GAS SAMPLE INJECTIONAPPARATUS Walter F. Gerdes, Lake Jackson, Tex., assignor to The DowChemical Company, Midland, Mich., a corporation of Delaware Filed Jan.6, 1967, Ser. No. 607,717 Int. Cl. G01n 31/08 US. Cl. 73-231 7 ClaimsABSTRACT OF THE DISCLOSURE and which dumps or discharges the accumulatedgas when a predetermined volume has accumulated. Hydraulic and gas flowsand liquid levels are arranged so that the discharge of the accumulatedgas sample is into the flowing stream of carrier gas. The device amountsto a chromatography type batching valve without moving parts, andwithout external operating means or timer. All functions are performedby hydraulic actuation.

Background of the invention This invention relates to apparatus forinjecting a sample of gaseous material into a stream or carrier gas, andparticularly to such a device which operates without any moving parts.

The present practice in automatic injection of gaseous samples intocarrier gas streams is to use a valve with one or more sliding surfaceswhich is actuated by an electric or penumatic actuator controlled by atimer or programmer and which moves so as to transfer a cavity ofprecise volume from a flowing stream of the sample material to theflowing stream of carrier gas. Such valves usually function with the useof moving parts, actuator, or timer and in accomplishing the injection amomentary interruption of carrier gas flow almost universally occurs.Such valves usually have small passageways which tend to plug withviscous portions of the sample.

Accordingly, a principal object of this invention is to provide animproved apparatus for injecting a sample of gaseous material into astream of carrier gas.

Another object of this invention is to provide an improved, more troublefree apparatus for injecting a sample of gaseous material into a streamof carrier gas.

A further object of this invention is to provide an improved, smootheracting apparatus for injecting a sample of gaseous material into astream of carrier gas.

Summary of the invention In accordance with this invention there isprovided a trap-accumulator in which liquid components of the sample tobe introduced are separated from the gaseous and the gas accumulated,and which dumps or discharges the accumulated gas when a predeterminedvolume has accumulated. Hydraulic and gas flows and liquid levels arearranged so that the discharge of the accumulated gas sample is into theflowing stream of carrier gas. The device performs the functions of achromatography type batching valve, but has no moving parts, and needsno external operating means or timer. All functions are performed byhydraulic actuation.

The invention, as well as additional objects and advantages thereof,will best be understood when the following detailed description is readin connection with the ice single sheet of drawing which shows, indiagrammatical form, apparatus in accordance with this invention.

Referring to the drawings, there is shown a sample injection apparatus,indicated generally by the numeral 10 which includes a looped sampleaccumulator, indicated generally by the numeral 12, comprising a hollowtubular loop 14, an input tube 16 and an output tube 18 extending belowand above the loop, respectively. The looped accumulator 12 is disposedwithin a gas light enclosure 20 which has an overflow tube 22 extendingupwardly from below the accumulator. The upper end 24 of the tube 22lies above the loop 14 but below the upper end 26 of the outlet tube 18.

The lower part of the overflow tube 22 extends through the bottom 28 ofthe enclosure 20 in sealed relationship therewith and turns upwardly,the upper end 30 of the tube 22 being disposed above the bottom of theloop 14 and below the top of the loop 14.

A carrier gas inlet tube 32 extends through and terminates just belowthe top 34 of the enclosure 20.

A carrier gas outlet tube 36 having an outwardly flared end 38 extendsthrough the top 34 of the enclosure 20 with the flared end 38 disposedabove and close to the output tube 18 of the accumulator .12. Anaccumulator feed tube 40 extends from above the top of the enclosure 20around and below the enclosure 20, enters through the bottom 28 of theenclosure 20, and is coupled to the input tube of the accumulator 12 bymeans of a suitable tubular coupling 42. The coupling 42 contains a bore44 which communicates with the interior of the inlet tube 16.

A sample feed tube 46, of substantially smaller diameter than thediameter of the tube 40, extends from above the inlet end 48, to a pointjust above the 'bore 44.

In operation, the overflow tube 22 maintains a constant level of liquidin the enclosure 20 except for a brief interval when the sample dumpsand the liquid level drops slightly.

Carrier gas flows into the upper part of the enclosure via entry tube 32and leaves (with or without being mixed with sample gas-depending onwhether or not the accumulator dumps sample gas at the moment) throughthe flared end of the tube 36.

Sample gas containing appreciable amounts of liquid enters through thesmall diameter tube 46 which extends through the tube 40 and slightlyabove the bore 44 in the coupling below the accumulator inlet tube 16.

Because the upper end 48 of the tube 46 extends above the liquidoverflow level in the enclosure 20 by an appreciable amount (h in thedrawing), liquid and/ or gas does not escape through the open end 48 oftube 40 even when the carrier gas in the enclosure 20 is under somepressure, unless that pressure is more than the head represented by h.

The end 26 of the output tube 18 of the accumulator 12 extends above theliquid level in the enclosure 20, so some impetus must be given theliquid in the accumulator in order to force it out the open end of theoutput tube 18.

As the combined liquid and gas sample enters the accumulator near thebottom, the gas portion rises as bubbles and the liquid portion goes outthe bore 44, thus building up a pressure of gas within the accumulator12. This forces some of the liquid in the right leg of the loop 14 down,and some of the liquid in the left leg of the loop 14 out the top. Whengas has accumulated to the point 50 shown in the sketch, any furtheraddition will blow the seal because further loss out the top of the leftleg will decrease the hydraulic head on the accumulation. Whereas liquidcoming into the accumulator previously has gone out the bore 44, at thetime the dump liquid enters the accumulator via bore 44 and forces allthe accumulated gas out of the accumulator 12. This results in a smalldrop in the level within enclosure 20,

with volume change exactly equal to that of the sample dumped. Thus theflow rate of the total gas out the carrier gas exit tube 36 is unchangedby the dump or insertion of the sample gas into the stream. The flowrate of carrier gas entering the device through tube 32 is not disturbedeither, since a volume of carrier gas equal to that of the sample mustbe used to fill the increase in head space within enclosure 20 caused bythe drop in liquid level. The dimensions of the accumulator are somewhatcritical. With liquids having surface tension similar to that of water,the accumulator internal diameter should be between 3 and 5 mm., withthe enlarged portions 42, 52 at least 5 mm. The diameter of bore 44should be at least equal to the inner diameter of the tube 16 toencourage access of water during the dump so that a smooth and completedump is achieved. Inner diameter of the central leg of the loop isincreased when it is desired to accumulate a larger sample, and heightof the loop may be increased, but diameters of the outer and horizontallegs are not increased. Glass has been found to be the best material forthe accumulator because it is more thoroughly wetted than are mostplastics. The sample tube 46 is commonly made from a fluorocarbon suchas Teflon. It is inserted only to the point shown in the drawing so thatit does not unnecessarily constrict the flow of water or liquid intoaccumulator 12 during the dump. When these precautions are observed, thespatial resolution or cleanness of the insertion of the sample into thecarrier stream is adequate for many purposes. In cases where there is noflow of liquid accompanying the flow of gaseous sample, the device maystill be used by filling the enclosure with a suitable liquid of lowviscosity and low volatility, or by trickling a small flow into thesystem independently of the sample and permitting it to overflow.

This invention has particular application to those cases in which arelatively large volume of sample is desired. Proper operation of thedevice is ditiicult to achieve with sample volumes less than about 1milliliter. There is no reasonable upper limit to the volume of samplewhich may be used. It has advantage primarily in those cases where thesample gas contains liquid, with viscous components which may cause avalve with sliding parts to malfunction or to leak. It has a furtheradvantage of being constructed entirely of glass and plastics such asfluorocarbons, so that such corrosive sample gases as wet chlorine haveno deleterious elfects on it. Since the interval at which the sample gasis dumped depends upon the rate at which it accumulates, it is necessaryto have a reasonably constant sample rate to the device. This is easilyachieved in practice.

What is claimed is:

1. Apparatus for injecting a sample of gaseous material into a stream ofcarrier gas, comprising:

(A) an enclosed container which is partially filled with liquid;

(B) an accumulator comprising parallel top and bottom tubular legs, atubular leg joining corresponding ends of said top and bottom tubularlegs, an input tubular leg having one end coupled to the other end ofsaid top leg and extends below said bottom leg, and an output tubularleg having an end coupled to the other end of said bottom leg, the otherend of said output leg being the only part of said accumulator extendingabove said liquid;

(C) tubular means extending from above said container to the input legof said accumulator;

(D) means coupling said tubular means to said input leg and having abore extending therethrough which communicates with said input leg;

(E) a liquid overflow tube, said tube extending from above said top legof said accumulator to below said accumulator and then terminatingbetween above said bottom leg by a distance approximately the distancebetween said liquid and the top of said container;

(F) a small diameter tube for introducing sample gas to saidaccumulator, said small diameter tube extending through and fittingloosely within said tubular means and terminating slightly above saidbore;

(G) means for introducing carrier gas into said container, and

(H) means adjacent to but spaced from the end of said output tubular legdisposed above said liquid for withdrawing gas from said enclosure.

2. Apparatus in accordance with claim 1, wherein said accumulator has anenlarged diameter part at the junction of said input tubular leg andsaid top leg.

3. Apparatus in accordance with claim 1, wherein said tubular parts ofsaid accumulator have an internal diameter of between 3 and 5millimeters.

4. Apparatus in accordance with claim 1, wherein the diameter of saidbore is equal to or greater than the internal diameter of the tubularparts of said accumulator.

5. Apparatus in accordance with claim 2, wherein the internal diameterof said enlarged part is at least 5 millimeters.

6. Apparatus in accordance with claim 1, wherein said accumulator ismade of glass.

7. Apparatus in accordance with claim 1, wherein said small diametertube is made of polytetrafluoroethylene.

References Cited UNITED STATES PATENTS 2,915,220 12/1959 Jacobson 222--32,973,117 2/1961 Conklin 222--3 RICHARD C. QUEISSER, Primary Examiner.

I. K. LUNSFORD, Assistant Examiner.

U.S. Cl. X.R. 73-422; 222-3 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3,435,661 April 1, 196

Walter F Gerdes rror appears in the above identified It is certifiedthat e 5 Patent are hereby corrected as patent and that said Lettershown below:

Column 1, line 38, "penumatic" line 5, "extends should read extendingshould read approximating should read pneumatic Column 4 line 18,"approximately" Signed and sealed this 14th day of April 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, J

Edward M. Fletcher, Jr.

Commissioner of Pateni Attesting Officer

